1. Field of the Invention
This invention relates to a battery pack and method of manufacture wherein a battery pack core is insert molded into a molded resin region. Specifically, this invention relates to a battery pack and method of manufacture that temporarily holds a battery pack core in a mold that forms the molded resin region, and attaches the molded resin region to the battery in a process step that forms the molded resin region.
2. Description of the Related Art
A prior art battery pack is assembled by inserting a battery pack core, which is an assembly of parts essential to the battery, into a plastic external case. Since a battery pack of this configuration is assembled while inserting and fastening the battery pack core into a fixed position in the external case, its manufacture is difficult. In contrast, a battery pack that does not use an external case has been developed. This type of battery pack is manufactured by insertion of a battery pack core when a molded resin region is formed. The molded resin region is equivalent to the external case. A battery pack with this configuration is manufactured by connecting parts essential to the battery as a battery pack core, temporarily holding the battery pack core in the mold cavity that forms the molded resin region, injecting molten synthetic resin into the mold cavity, and as a result, inserting the battery pack core into the injected synthetic resin. Since the battery can be fixed in place in the battery pack during molded resin region formation, the external case can be omitted and the battery pack can be efficiently manufactured in quantity. The molded resin region not only forms part of the external case of the battery pack, it also serves to solidly attach various parts connected to the battery into a single unit. Consequently, since the battery pack core can be fixed in place when the molded resin region is formed, the battery pack has the characteristic that it can be efficiently and inexpensively manufactured in quantity.
In a battery pack of this configuration, the exhaust outlet of the safety valve provided on the battery is closed off by the molded resin region. Gas discharged from an open safety valve escapes to the outside through gaps formed between the battery and the molded resin region. Accordingly, gaps are generated between the battery and the molded resin region attached to the battery during molding by pressure from gas discharged from the safety valve. In this type of battery pack, when the battery pack core is temporarily held in the mold cavity and molten synthetic resin is injected into the mold cavity, the molten synthetic resin can destroy the safety valve. To prevent this detrimental effect, a battery pack has been developed that forms the molded resin region with the exhaust outlet of the safety valve covered by an insulating cover (see Japanese Patent Laid-Open Publication No. 2004-213931).